The lateral access approach is frequently utilized to deliver interbody fusion cages to the lumbar spine. In comparison to conventional anterior or posterior approaches to the lumbar spine, the lateral approach is thought to minimize posterior and/or anterior tissue damage as well as reduce surgery time, associated blood loss, vascular damage and infection risk.
When multi-level access to the spine is provided through a single minimal access port, the insertion trajectory to the superior and inferior levels is not parallel to the vertebral endplates at those levels.
In addition, direct lateral access parallel to the L4/5 and L5/S1 levels is not achieved due to the presence of the iliac crest directly lateral to those levels. Accordingly, the angled trajectory required for lateral access to these lower levels risks the cages being implanted at a “malpositioned” angle that prevents balanced loading across the vertebral endplates and spine. This “malpositioned” access, associated endplate damage and device placement can initiate subsidence, loss of correction, collapse of the retracted disc space, and result in spinal instability. This may result in increased surgery time, a higher difficulty in insertion and muscle damage.
US2008-0133012 (“McGuckin”) discloses a spinal implant having a series of sections or units hinged together and a balloon connected to at least some of the sections, the balloon having a curved configuration. The implant has a first delivery configuration and a second curved placement configuration, wherein it has a more linear configuration in the first delivery configuration than in the second curved configuration. The implant assumes the first delivery configuration during delivery to the disc space and maintains the curved configuration after placement within the disc space. The curved configuration can result from filling or expanding the balloon.
US2006-0142858 (“Colleran”) discloses methods and apparatuses for maintaining spacing between neighboring vertebrae, while minimizing the size of the surgical opening required. In one embodiment, an expandable spinal implant is made having movable parts that can arranged so as to have a small maximum cross-sectional width so that the cage can be inserted through a smaller surgical opening and then expanded to a full size assembly between the vertebrae.
U.S. Pat. No. 6,387,130 (“Stone”) discloses a method of positioning a plurality of intervertebral implants in a patient's intervertebral space, comprising: introducing an elongated member into the patient's intervertebral space; and sequentially advancing a plurality of intervertebral implants over the elongated member and into the patient's intervertebral space, the plurality of intervertebral implants each having at least one hole passing therethrough, with the elongated member received through the holes passing through each of the plurality of implants.
US Patent Publication No. 2008-0125865 (Custom Spine) discloses an intervertebral fusion device that articulates in the horizontal plane.
US Patent Publication No 2009-0062807 (Vermillion Technologies, LLC) discloses a method for performing percutaneous interbody preparation and placement of an interbody device from a posterolateral orientation via a cannulated, self-distracting tool with a guide mechanism.
US Patent Application 2011-0125266 (Rogers) discloses lateral cage that vertically flex.